In general, the present invention is directed to pyrometallurgical systems wherein it is desired to entrain particulate matter into a molten slag. In particular, the invention relates to an improved design for a mechanical stirrer of the type described in U.S. Pat. No. 3,861,660, issued Jan. 21, 1975, and owned by the Assignee of the present invention.
According to the present invention, it has been realized that certain groups of stirrer parameters are important in optimizing the desired results in pyrometallurgical systems in which (a) particulate solid-liquid contacting is required and (b) liquid-liquid contacting is required. The present invention is directed to the former improvements and my contemporaneously filed U.S. patent application entitled "Pyrometallurgical System for Liquid-Liquid Contacting" is directed to the latter improvements.
The economic competitiveness of pyrometallurgical slag cleaning, as compared to milling-flotation, depends upon rapid reaction rates which, in turn, depend upon maximizing the entrainment of the particulate reductant (e.g., coal) in the liquid slag. The rapid entrainment of such a reductant into the liquid slag is rendered difficult by the concommitent requirement of not entraining gas along with the particulate solid. Furthermore, the entrainment is also difficult since it involves the entraining of a low density particulate solid floating on the surface of a high density liquid slag, thereby requiring that the inherent high buoyancy of the particulate matter be overcome.
It is thus a principle object of the present invention to provide, for use in a pyrometallurgical system, an improved stirrer or an array of stirrers which will rapidly and efficiently entrain a low density particulate solid into a high density liquid.
It is a further object to provide such a stirrer or an array of stirrers which will entrain the particulate solid without entraining substantial quantities of gas as well and without causing substantial damage or wear to the walls of the vessel which contains the liquid.